How to set the output voltage for the TPS92201

[mangoByte]

Hello everyone.

This is my first post. I am working on a LED lamp project for which I have chosen the TPS92201 as the LED driver. I would like the output current to be 800mA. So according to the datasheet I have chosen a 0.125m ohm resistor. What I do not understand is how to set the output voltage. In section 8.2.2.2, there is a formula given, which says that a R2 resistor needs to be used. There is no R2 resistor shown in the schematic. Confusingly in the equation in 8.2.2.2 V_FB=0.6V but in section 7.3.5, it says that V_FB is typically 0.1V.

I would like to know how to correctly use this IC for an output current of 0.8A and ouput voltage of 3V. This is my first project with such a complexity, so please excuse me for being a noob. I appreciate any help.



This is the datasheet: https://www.ti.com/lit/ds/symlink/tps92201.pdf

[Zero999]

You don't. The output voltage is the forward voltage of the LED(s) plus the feedback voltage. The feedback volage is typically 0.1V, so for 400mA:

V = 0.1V
I = 0.4A

R = V/I = 0.1/0.4 = 0.25R.

It's a constant current power supply. It regulates the current not the voltage. The voltage is determined by the characteristics of the LEDs, which depend on the temperature and current. I have only skimmed the data sheet, but if there's a calculation involving the output votlage, just use the nominal forward voltage given on the LED data sheet, plus the reference voltage.

[mangoByte]

Oh that makes total sense. I was just confused because the datasheet has section that mentions setting the output voltage with the R2 resistor, that is not shown in the schematic. Thank you very much

[SiliconWizard]

Oh that makes total sense. I was just confused because the datasheet has section that mentions setting the output voltage with the R2 resistor, that is not shown in the schematic. Thank you very much

That's something others have noticed with those datasheets from TI. Many of their buck LED drivers have similar confusing paragraphs which appear C/C from other datasheets for conventional buck converters.

[Zero999]

Oh that makes total sense. I was just confused because the datasheet has section that mentions setting the output voltage with the R2 resistor, that is not shown in the schematic. Thank you very much

That's something others have noticed with those datasheets from TI. Many of their buck LED drivers have similar confusing paragraphs which appear C/C from other datasheets for conventional buck converters.

Could they be using AI to generate them?

[Nominal Animal]

I described the issues with the TPS92201 datasheet in this post here, and reported it to TI here; the corrected datasheet should be available in a few weeks.

[mark03]

I described the issues with the TPS92201 datasheet in this post here, and reported it to TI here; the corrected datasheet should be available in a few weeks.

Ha... looks like it never was 

Do we believe the pins are actually reversed between the two packages?  In other words, is one of the pinouts wrong or is one of the suggested layouts wrong?

EDIT: nevermind, I see one of the TI guys confirmed your layout, i.e. the WSON and SOT versions really are reversed---weird.